Re: CHAT: Ultraviolet (was: Orange)

>From: John Cowan <jcowan@...>
>
>Lars Henrik Mathiesen scripsit:
>
> > The source I read didn't go into stuff like how many different colours
> > he perceived in the new wavelengths, or how much it changed the look
> > of everyday objects --- more that his colleagues though it was neat
> > how he could calibrate their UV spectrometers without a photometer.
>
>People in this position (and they are not rare; the treatment
>for cataract is to remove the lens, and most of us get cataracts in
>our 80s if not sooner) don't actually see new colors: they just see
>purple further to the right in a spectrum, in an area where the rest
>of us see nothing.  Perhaps if one's lenses were removed *early*
>enough, while the brain has the flexibility to adapt ... who knows?
>
You just reminded me of a lecture I attended by Paul Churchland about a
neural network that they trained in colour perception.  I have a feeling
that our brains are simply wired to perceive colour a certain way (limited
by number and pattern of neuronal connections)- even if the lenses were
removed early enough, the individual in question probably wouldn't see any
"new" colours - although may have a finer perception of them and / or a
wider range.  Even if we could see microwaves, they'd probably still look
purple (although if we could, then UV would probably look more blue or maybe
even greenish).

However - the stereoscopic cells in the visual cortex are dependent on eye
development - we detect distance / perspective using several visual clues,
as well as special cells specifically adapted for the task.  People with
congenital myopia, astigmatism, etc., or whose eyes develop a little more
slowly than normal, will have undeveloped stereoscopic cells.  It isn't much
of an impairment, except that without stereoscopic cells a person probably
wouldn't be a very good fighter pilot or baseball player - and among other
things, will never be able to see the secret picture in one of those "Magic
Eye" illustrations, no matter how hard they try.

Andy


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